Circuits for grid controlled gas filled electron tubes



Oct. 20, 1942. F. G. ALLDE 2 2,299,212

CIRCUITS FOR GRID CONTRQLLED GAS FILLED ELECTRON TUBES Filed Sept. 7,1940 GAS FILLED INVENTOR. Frederic/f G. Hal/de ms Arr-aways PatentedOct. 20, 1942 CIRCUITS FOR GRID CONTROLLED GAS FILLED ELECTRON TUBESFrederick G. Hallden, Bellerose, N. Y., assignor to Postal,Telegraph-Cable Company (New York), New York, N. Y., a corporation ofNew York Application, September 7, 1940, Serial N 0. 355,715

6 Claims.

The present invention relates to circuits for grid controlled gas filledelectron tubes, and particularly to circuits which make it possible toutilize such tubes for causing current reversals at high speeds.

It is an object of the invention to provide a circuit for gridcontrolled electron tubes of the gas filled type whereby these tubes aybe u lized to give controlled reversals at high speed.

It is another object of the invention to utilize a pair of tubes and toprovide a circuit which will make it possible to fire one of the tubesand at the same time extinguish the other tube of the pair quickly.

It is a further object of the invention to provide a circuit asmentioned above in which the apparatus for accomplishing the purposesmentioned shall be simple and inexpensive.

Further objects and features of the invention will appear when thefollowing description is considered in connection with the appendeddrawing, in which Figure 1 is a diagram showing the circuit connectionsfor utilizing two gas filled grid controlled electron tubes as apolarity reversing means; and

Figure 2 is a diagram similar to Figure 1 showing in addition, however,one method of connecting the tubes to a control circuit, and biasingbatteries for biasing the grids of the two tubes. The method shown inthis figure may be utilized for the repeating of polar telegraphsignals.

Referring now to Figure 1, there are two grid controlled gas filledelectron tubes I and 20. These electron tubes may be of either the hotcathode or cold cathode type and may be either negative, positive, orcombination control tubes. In the present instance, however, it isassumed that the tubes are of the hot cathode type, and also of thenegative control type. Tube II] has an anode-cathode circuit whichincludes a resistance I I, current source I2, load I3 and resistance II, as well as a grid cathode circuit which includes resistance I4 and asource of control potential.

In a similar manner the tube isprovided with an anode-cathode circuitcomprising resistance 2I, current source 22, load I3, and resistance 24,and with a grid cathode circuit including resistance 24 and a source ofcontrol po-. tential 25. It willbe seen that the .load I3 is common tothe output circuits of the two tubes I0 and 20, and that therefore ifone tube can be caused to extinguish its arc whenever the other tubeignites, then current reversals may be produced in the load I3.

I I and 24, together with the condensers 30 and 3 I, the former of whichis connected across the anodes and the latter across the cathodes of thetwo tubes, combine to produce circuit conditions which cause theextinction of one tube of the pair in a time period of the order ofmicro-seconds after ignition of the other tube.

Figure 2 shows a circuit substantially identical with that of Figure 1except that in Figure 2 the grid circuits for the two tubes includebiasin batteries I6 and 26 and secondary windings I! and 21 of atransformer 32. The primary winding 33 of transformer 32 is connected toa controlling source Which may be a telegraph line. The control signalsof the primary winding appear in the secondaries of the transformer asvoltages, which are efiective in causing the firing and thus theextinction of the tubes in a proper manner in response to the controlsignal.

Without limiting myself as to the mode of operation of the circuitdescribed, or as to the theory of its operation, I believe that thecircuit operation is as follows:

If a potential is applied to the winding 33 of transformer 32, thispotential may generate a potential with positive polarity toward thegrid in transformer winding I1 and simultaneously one of negativepolarity toward the grid in transformer winding 21. If theimpulse inwinding I1 is sufficiently large it will cause tube It] to be fired. Ofcourse, the negative impulse in winding 2'! will apply a negativevoltage to the grid of tube 29 which will have no effect on this tube.

Due to the ignition of tube I0, current will fiow through a circuitincluding battery I2, resistance II, tube I0, resistance I4, conductor28, terminal 36, line 34, any load which there may be on that line, andterminal 35. Due to flow of current in this circuit there will bevoltages applied to the various circuit components, the voltages acrosscondenser 30 being equal to the load voltage (i. e., the voltage acrossterminals 35 and 35) plus the voltage across resistance II. Condenser 30will be charged in such a manner that the terminal adjacent tube I0 willbe negative and that adjacent tube 20 will be positive.

Condenser 3| will also acquire a charge. The potential across thiscondenser will be the potential of battery I2 minus the voltage dropsacross resistance II and tube I0. The charge on this condenser will besuch that the terminals adjacent the cathode of tube ID will be positiveand that adjacent the cathode of tube 20 will be negative.

In the present instance the resistances II, 2|,

If, now, a control signal of opposite polarity is from battery l2through conductor I8, resistance 24, tube 20, resistance 2|, battery 22,conductor 28, resistance l4, tube l0, resistance H, and back to batteryI2. I

Due to this condition, the voltage across terminals 35 and 36, or inother words the voltage across the line or load, becomes zero, and inaddition the voltages applied to condensers 30 and 3| become zero.However, these condensers have been charged, as was explained before,and since the ignition of tube takes place in a few micro-seconds,condensers 30 and 3| retain substantially all of their original chargeand are therefore at the voltages mentioned hereinabove.

The voltage which exists across tube H] at this instant may be found byadding the voltages around any loop of the circuit starting and endingat tube |0. Since it is the effect of the voltages across condensers 30and 3| which is of primary interest, the loop from tube I0 going throughcondenser 30, tube 20, condenser 3|, and back to the cathode of tube IDwill be considered.

As explained, the polarity of condenser 30 was negative toward the anodeof tube l0 and that of condenser 3| positive toward the cathode of tubeH]. Therefore the potential between the cathode and anode of tube I0must be the voltage of condenser 30 plus the voltage of condenser 3|,minus the'internal voltage drop within tube 20. The voltage drop Withinthe tube is low relative to the voltages across condensers 30 and 3|,and therefore the polarity of the Voltage on tube II] will be negativeat the anode and positive at the cathode. This will, of course, beeffective to stop conduction through tube In and permit the grid of thattube to regain control.

At this time condensers 30 and 3| will discharge and cause a negativepotential to be applied to the anode and a positive potential to thecathode of tube In, thereby stopping conduction. The discharge currentwill in this case flow through resistance l4 and cause a high negativepotential on the grid of tube I0.

However, although the action above described occurs almost instantlywhen tube 20 ignites, the grid of tube [0 has not actually reacquiredcontrol of the tube until the gas in the tube is completely de-ionized,or until the ions are assembled at a point Where they will not causeresumption of conduction when the anode again becomes positive. It iscommon practice to insert a negatively charged electrode in an ionchamber to prevent the resumption of conduction due to the anodebecoming positive. I have found that the grid serves this purpose when,as described above, the grid is made highly negative by the discharge ofcondenser 3| through resistance M, which is in the grid circuit.

By the time that the discharge and recharging of condensers 30 and 3| inthe opposite direction is complete, the grid of tube H] has regainedcomplete control of that tube and the reappearance of a positivepotential at the anode relative to the cathode will fail to fire thetube. Tube 20 is now conducting and its anode current has reached asteady state, which is exactly the condition which existed after thefiring of tube l0, except that now tube 20 is conducting instead of tubeIii, the direction of current flow through the load is reversed, and thepolarity of the charging potential across condensers 30 and 3| isreversed. These polarities bear the same relation to tube 20 that theformer ones did to tube l0, so that when the next signal reversal isreceived on the incoming line a positive pulse of voltage in the gridcircuit of tube 0 will be produced, and tube ID will be fired while tube20 will be extinguished.

'It will be seen that upon each reversal a current impulse ofcorresponding polarity is sent into the outgoing line 34 or the loadresistance l3 as the case may be.

It is, of course, assumed that the various resistances and condensersare selected toproperly perform their functions, but it is to beunderstood that the values of these elements are not critical and thaton the contrary it is the combination of resistances ll, 2|, I4 and 24with the condensers 3|! and 3| which brings about the result achieved,rather than any particular or critical values of these elements.

Although it is preferable to utilize all the circuit elements mentioned,the circuit is operable when resistances H and 2| are omitted.

It is, of course, obvious that the Values of the various resistances andcondensers will vary in accordance with the particular tubes utilizedand likewise obvious that the values of the resistances associated withthe two tubes must be substantially equal if similar batteries I2 and 22are to be utilized and the positive and negative outgoing impulses areto be substantially identical with respect to their amplitude.

While I have shown a preferred embodiment of my invention, it is to beunderstood that many modifications and alterations might be made withinthe scope of the invention, and therefore I do not wish to be limited bythe foregoing description but on the contrary wish to have my inventionlimited only by the appended claims.

What I claim is:

1. In electronic reversing switch apparatus, in combination, twogrid-controlled gas filled electron tubes, each having anode, cathodeand grid electrodes, an input circuit extending from the 1 grid to thecathode of each tube, each said circuit comprising a source of gridbias, a signal source and a series resistor, one end of said resistorbeing connected to said cathode, an output circuit extending from anodeto cathode of each tube, each said output circuit comprising a seriesresistor one end of which is connected to the anode, a battery, a load,and a return to cathode through said series input resistor, said loadbeing common to the output circuits and said other elements beingindividual to the particular output circuit, a capacity interconnectingthe cathodes of said tubes and a capacity interconnecting the anodes ofsaid tubes.

2. In an electronic device for producing in a load circuit currentreversals in accordance with received signals, in combination, two gridcontrolled gas filled electron tubes each having anode, cathode andcontrol electrodes, a single load circuit connected to the anodes andcathodes of both said tubes, an input circuit extending from grid tocathode of each tube, each input circuit including means for applyingreceived signal potentials to the corresponding grid, said applyingmeans being reversed in one input circuit with respect to the other,whereby a signal of given polarity will tend to render one tubeconductin and a signal of opposite polarity will tend to render theother tube conducting, an output circuit for each tube, each circuitcomprising a source of potential and said common load, and a capacityconnecting the anode of one tube to the anode of the other, saidcapacity being discharged and charged in the opposite direction uponreversals of the received signal and consequent ignition of the secondof the two tubes, said reversal acting to reduce the anode voltage ofthe first tube to a value below that at which conduction can continue.

3. In an electronic device for producing in a load circuit currentreversals in accordance with received signals, in combination, two gridcontrolled gas filled electron tubes each having anode, cathode andcontrol electrodes, a load circuit connected to the anodes and cathodesof both said tubes, an input circuit extending from grid to cathode ofeach tube, each input circuit including means for applying receivedsignal potentials to the corresponding grid, said applying means beingreversed in one input circuit with respect to the other, whereby asignal of given polarity will tend to render one tube conducting and asignal of opposite polarity will tend to render the other tubeconducting, an output circuit for each tube, each output circuitcomprising a source of potential, said common load, and a resistor, saidresistor being likewise included in the corresponding input circuit, anda capacity connecting the anode of one tube to the anode of the other,said capacity being discharged and charged in the opposite directionupon the reversals of the received signal and consequent ignition of thesecond of the two tubes, said reversal acting to reduce the anodevoltage of the first tube to a value below that at which conduction cancontinue.

4. In an electronic device for producing in a load circuit currentreversals in accordance with received signals, in combination, two gridcontrolled gas filled electron tubes, each having anode, cathode andcontrol electrodes, a load circuit connected to the anodes and cathodesof both said tubes, an input circuit extending from grid to cathode ofeach tube, each input circuit including means for applying receivedsignal potentials to the corresponding grid, said applying means beingreversed in one input circuit with respect to the other, whereby asignal of given polarity will tend to render one tube conducting and asignal of opposite polarity will tend to render the other tubeconducting, an output circuit for each tube, each output circuitcomprising a source of potential, said common load, and a resistor, saidresistor being likewise included in the corresponding input circuit, acapacity connected from the cathode of one tube to the cathode of theother, said capacity being discharged and re charged in the oppositedirection upon reversal of the received signals and consequent ignitionof the second tube, said discharge flowing through said series inputresistor and acting to raise the cathode potential of the first tube tosuch a value with respect to the anode of that tube that conductioncannot continue.

5. In an electronic device for producing in a load circuit currentreversals in accordance with received signals, in combination, two gridcontrolled gas filled electron tubes each having anode, cathode andcontrol electrodes, a load circuit connected to the anodes and cathodesof both said tubes, an input circuit extending from grid to cathode ofeach tube, each input circuit in cluding means for applying receivedsignal potentials to the corresponding grid, said applying means beingreversed in one input circuit with respect to the other, whereby asignal of given polarity will tend to render one tube conducting and asignal of opposite polarity will tend to render the other tubeconducting, an output circuit for each tube, a capacity connecting theanode of one tube to the anode of the other, said capacity beingdischarged and charged in the opposite direction upon reversals of thereceived signal and consequent ignition of the second of the two tubes,an output circuit for each tube, each output circuit comprising a sourceof potential, said common load, and a resistor, said resistor beinglikewise included in the corresponding input circuit, said reversalacting to reduce the anode voltage of the first tube, and a capacityconnected from the cathode of one tube to the cathode of the other, saidcapacity being discharged and charged in the opposite direction uponreversal of the received signals and consequent ignition of the secondtube, said discharge taking place through the said series input resistorand acting to raise the cathode potential of the first tube, saidreduction in anode potential and increase in cathode potential of thefirst tube together acting to render said first tube nonconducting andto maintain it in that condition.

6. In an electronic device for producing in a load circuit currentreversals in accordance with received signals, in combination, two gridcontrolled gas filled electron tubes each havin anode, cathode andcontrol electrodes, a load circuit connected to the anodes and cathodesof both said tubes, an input circuit extending from grid to cathode ofeach tube, each input circuit including means for applying receivedsignal potentials to the corresponding grid, said applying means beingreversed in one input circuit with respect to the other, whereby asignal of given polarity Will tend to render one tube conducting and asignal of opposite polarity will tend to render the other tubeconducting, an output circuit for each tube, each said output circuitcomprising a source of potential, two resistances, one of which is alsoincluded in the corresponding input circuit, and said common load, and acapacity connecting the anode of one tube to the anode of the other,said capacity being discharged and charged in the op posite directionupon reversals of the received signal and consequent ignition of thesecond of the two tubes, said reversal of charge acting to produce apotential drop through said anode resistance of said first tube tothereby reduce the anode potential of that tube to a value below that atwhich conduction can occur.

FREDERICK G. HALLDEN.

